Fuse plug



March 1, 1932. 'r. w. MERTZ 1,847,970

FUSE PLUG Filed Dec. 13, 1950 2 Sheets-Sheet 1 Inventor Tam W 1%??? AHome y March 1, 1932. T. w. MERTZ 1,847,970

FUSE PLUG Filed Dec. 13, 1930 2 Sheets-Sheet I 2 Invenior 7714mm .sWllrfz A Home y UNITED STATES Patented Mar. 1, 1932 PATENT QFFICE' mommm, orwmas'rm srzames wnsr vmemm [ruse PL G] Application'flled December13, .1930, Serial No. 502,198.

. sign. i

It isun object of this invention to provide a fuse plug of the typereferred to, which automatically prevents the over-fusing of the samewith the consequent damage to the circuit, though it may be underfused,by providing certain features of novelty and construction which will'beset out below.

it is also anobject of this invention to provide a fuse plug of thetypeldescribed, which cannot easily be removed,since it is provided to belocked in place.

It is also an object of this invention to provide a fuse plug ofthe typedescribed, which cannot be bridged, and hence is safe in operation andprotected from premediuse of the fuse sockets with resultant creasedsafety-and convenience. V I It also anobj-ect of this inventionto'provide a 'fuse plugof the type described, which may be re-fusedwithout removing the same from its associationin a circuit.

These and ther objects of the invention, Width of ,thiscm or Slot 10 isas) its nature, and composition and arrangement and combination of partswill be readi ly understood by any one acquainted with the art to whichthis invention relatesupon consulting the following descriptions of thedrawings wherein .251115 improved ifuse plug.

for association with the ordinary exteriornportipnyfi' of the shell ,5.

F i'gn'2 anj-end View thereof, taken from the right of Fig; 1 and F ig.3 is a longitudinalverticalcross sect'ional View taken on the line 33 ofFig.2;

Fig. 4 is a-transverse'vertical cross seetion- 68 al View approximatelyon-the line 4- of 3, and* i 5 is 'a' similar vertical transverse crosssectional view approximately on the line-5-'-'5 ofFig-3. I

F i 6 is alongitudinal' vertical and approximately central sectionalview likethat' of Fig. 3, but Fig. 6 shows the core with drawn outwardly,of the shell of the plug.

Fig.7 showsan elevationalview similar 65 to Fig. 1, withtheeXceptiOnthat Fig/7' shows the core withdrawn-from the shell and the slots in thecore and in the shellin alined position. f

Fig. .8 is an elevational view ofthefcore it- 70 self in the position inis found in Fig. "9 is a similar viewto' Fig. 8, takenatj right anglesthereto, on the longitudinal axis. ofthe core. f -T 1 71-? Referring indetail to the drawings, the numeral'fi designates generally the shell:of the fuse plu which jm ay have the" screw, threaded portion 6an-d'as'sociated central con? tact thereon 7. The numeral "8 designatesgenerally the core of my fuseplug which is adapted to have a portionprojected into, thatis, telescoped into the. shell 5'. The core isprovided with a handle portion 9 something inthe'form of a door knob.The shell 5 c'onsists of 1a hollow cylindrical body having one endclosed and theother openedto receive I the said coresl'idablyortelescopically therein. As seen in Fig. 4 an intermediate portion ofthe {shell 5]is transversely cut to a distance 9. half way through asindicated at 10. i'lhe elude from positioning therein a largersize fusewirethan-the stated capacity of the par; ticular plug. ReferringtoFig.::3, it will be 9?: observed that the immerals Hand 12 refer to apair of diametrically opposed contacts which are connected by means ofWires 13 and Figure '1 1S ageneral side relevational view.

14 led to the contact -7 and to the screw mo At 90 from the terminals ofthe slot 10, the shell 5 carries a pin or dowel 15 projecting inwardlyto engage certain portions of the core to be described. As observed inFig. 1, the pin 15 is disposed near the outer end of the shell 5.

As before stated, the core 8 though snugly fitted, slides or telescopeswithin the shell 5, but the withdrawal movement of the core 8 is limitedby the pin 15 which engages in a slot 16 formed from a point within theouter end of the core to an intermediate portion thereof where itcommunicates with the peripheral groove 17.

It will. be understood that when the pin 15 is engaged in the slot 16,the core may be withdrawn from the shell until the pin 15 abuts the rearwall of the peripheral slot 17 but no farther. It will also beunderstood that the core may not be rotated except when the )in 15 isdisposed in the peripheral slot 17. he reason for the provision of thestructure just described will be better understood as the descriptionproceeds further.

It will be observed in the drawings that the inward end of the core 8 isformed with slight taper 18. It will also be observed that dimetricallydisposed at 90 from the slots 16 there is provided near the inward endof the core a relatively large cylindrical bore 19 formed completelythrough the core.

A slot 20 at right angles to the bore 19 communicates with saidcylindrical bore as particularly well seen in Fig. 9.

As already stated contacts 11 and 12 are exposed at diametricallyopposite points in the interior wall of the shell Somewhat outward ofthe contacts 11 and 12, there are provided other and similarlydiametrically oppositely placed metal pieces 21, 22 immedi atelyadjacent the cut or slot 10 as particularly well seen in Fig. 4. Throughthe core 8 is a small longitudinal bore 23 in which is loosely slidablea rod 24 having a disk or the like 25 disposed on its inward end whichis arranged in a depression or recess 26 in the wall of the cylindricalbore 19.

The outer end of the bar 24 has a handle 27. At 90 from the terminals ofthe slot or cut 10 in the shell there is provided a longitudinal slot 28which extends from an intermediate portion of the shell to the endthereof.

With the arrangement described above, it will be obvious that bywithdrawing the core the required distance it may be rotated to bringits enlarged cylindrical bore 19 into registry with the enlarged slot 28in the shell as shown in Fig. 7 In this position, it is obvious that anyfuse wire or strip which may lie in a U-shaped form over the tapered endof the core as shown in Fig. 3, may be easily removed.

To refuse the plug, the core is withdrawn to the limit from the shelland the proper fuse wire or the like passed through the slot 10 so thatit extends on a diameter of the shell. It is part of my invention toprovide a fuse plug of the type described which is adapted to cut itsown fuse wire, and, therefore, the metallic pieces 21 and 22 areprovided to shear a length of the proper dimension upon the forcing ofthe core inwardly against said wire strip, in which action the shoulder31 cooper-a es with the shearing blocks 21 and 22 to cut the fuse link.

As shown in Fig. 3, the continued inward movement of the core 8 carriesthe fuse strip wire 29, once it has been sheared, and deforms it fromthe position shown in Fig. (3. It will be seen that the fuse wire inFig. 3 has conformed itself to the tapered portion of the tapered slots30 leading from the outward wall of the cylindrical bore 19, in whichposition the limit of the motion of the bore inward will place the endsof the fuse wire or strip firmly in contact with the contacts 11 and 12.The portions between the ends of the slots 30 and the peripheral groove17 form the shearing blocks 31 for cooperation with the elements 11 and12.

It will be observed that should the wire or strip attempted to be usedin re-fusing the plug be too hard or be of material of a greatertenacity than the proper kind of fuse wire or strip, the same would notbe cut readily by the shearing action of the plug and shell and theinferior or improper charactor of the fusing material attempted to beinserted would be immediately evidenced, by the refusal to shear or toproperly conform itself, or producing a jam.

WVhen the strip or wire is in proper position and not blown out, the rod24; will indicate this condition by its refusal to be freely projectedinto the cylindrical bore 19. Whereas, should the fuse material be blownout, the rod 24 may be freely pushed in up to its limit, and this willinvariably indicate the condition of the fuse material,withoutnecessitating the taking apart of the fuse plug.

' The method of discharging the blown fuse material has already beendescribed and shown in the drawings, particularly in Fig. 7, and thesiu'iplicit-y of tho removing operation will now be clearly seen. Anadditional feature of interest is the provision of l'llOtdPO-l or wedgescrews which are adapted to expand the ferrule (5 against the interiorof the socket receptor whereby the plug assembly is locked securely tothe panei, mounting board or the like.

It will now be recognized that I have pro vided a very efficient anddesirable fuse plug of the type described presenting features of noveltyand advantage resulting in convenience and safety factors not heretoforeachieved in a device of the character described. The extreme andadmirable usefulness and convenience of my invention cannot plug and hasother advantages and features of novelty as set out herein. 7

It isto be definitely understood that I do not desire to-limit' theapplication of this invention to the particular modifications set outherein, toillustrate the principles thereof, and any change or changes.may be made in structure and arrangement of parts as well asinmaterials, within thespirit and scope of theinvention;

Having thus described my invention, what IclaimasMwisz- I 1. 'A safetyfuse plug-of the type described comprising a tubular shell having alongitudinal slot and a core provided with a trans versebore and adaptedto telescope into said shell, apin on the shell, said core havinggrooves adapted to be engaged-by the pin for limiting the withdrawingthereof from --the shell but permitting relative rotation, a

piece of fuse Wire, said bore in the core being registrable with saidlongitudinal slot to permit withdrawing and replacing the fuse wire fromthe interior of the shell, said shell having a tIfiIlSVGI'SGzSlltthrough which said fuse wire isto be passed to the interior of the shellfor limiting the size of fuse wire to be used in the plug.

2. A safety fuse plug of the type described comprising a tubular shellhaving one end closed and provided with a screw threaded socket engagingferrule, and an end contact and having its end open, a pair of contactsin the shell connected to said ferrule and end contact, a core adaptedto be telescoped into said shell, a piece of fuse wire, said core havinga transverse bore adapted to receive a length of the fuse wire, saidshell having a transverse measuring slit for limiting the size of fusewire to be secured in said bore, a length of fuse wire, placed in saidbore and being adapted to be sheared between the sides of the bore andone edge of said slit so as to cut the fuse wire to the properlength'upon inward movement of the core, said core adapted to movefurther inwardly after shearing the fuse wire to bend the end portionsof the cut length of fuse wire and wedge the ends thereof between thecore and the "pair of contacts in the shell.

3. A safety fuse plug of the type described comprising a tubular shellhaving one end closed and provided with a screw threaded socket engagingferrule and an end contact,

a pair of contacts in the shell and connected 'to receive said fusewire, said shell having a transverse measuring slit through which saidfuse wire must pass into said bore, said fuse wire being adapted to besheared between the sides of the core and one edge of said slit, so asto cut the fuse wire to the required length upon inward movement of thecore, said core being adapted tomove further inwardly after'havingsheared the fuse wire so as to bend the end portions of the cut lengthof fuse wire and wedge the ends there of between the core and the pairof contacts in the shell, and a fuse wire tester rod longitudinallymovable in said core for contacting the intermediate (portion of alength of fuse wire sopositione 4. A safety fuse plug of the typedescribed comprising a tubular shell having one end closed and providedwith a screw threaded socket engaging ferrule and an end contact, W

and havinglts other end open, acore, adapt= ed to telescope'into saidshell, :1 piece of fuse wire, said core" having a transverse bore,

adapted to receive said fuse-wire, said shell having a transversemeasuring slit through which said fuse wire is to be passed into saidbore, said fuse wire being adapted to be" sheared between the sides ofthe core and one edgeof said measuring slitso as to cut the fuse wire tothe required length upon inward 1y moving the core, said. corebeingadapted to be further moved inwardly, to bend the end portions ofthe cut len th of fuse wire and wedge them between t e core and the pairof contacts in the shell, a fuse wire tester rod longitudinally movableinsaid core for contacting the intermediate portion of a length of fusewire so positioned, said shell being provided with a longitudinal slotopposite said measuring slit registrable with said transverse bore inthe core to permitth removal of so positioned fuse wire.

"5'. A safety fuse plug of the type described comprising a tubular shellhaving one end' closed and provided with a screw threaded socketengaging ferrule and an end contact and having its other and open, acore adapted to telescope into said shell, a piece of fuse wife, saidcore having a transverse bore adapted to'reecive said fuse who, saidshell having a transverse measuring slit through which said fuse wire isto be passed into said bore, said fuse wire being then adapted to besheared-betweenthe sides of the core and the of the so positioned fusewire, said shell be- 1 ing provided with a longitudinal-slot oppo-- sitesaid measuring slit registrable with said transverse bore in the core topermit the removal of said so positioned fuse wire, said core beingformed with a transverse peripheral groove, and a longitudinal grooverun- L'ning from a point within the outward end of the core into saidperipheral groove, a pin projected from the wall of the shell forengagement in said peripheral and longitudinal grooves for permittingrelative rota- .tion of the shell and core while limiting completewithdrawal of the core from the shell.

6. A safety fuse plug of the type described comprising a tubular shellhaving one end closed and provided with a screw threaded socket engagingferrule and an end contact core, said core being adapted to be movedfurther inwardly so as to bend the end portions of the cut length offusewire and wedge the ends thereof between the core and the pair ofcontacts, a fuse wire tester rod longi-v tudinally movable in said corefor contacting the intermediate portion of the fuse wire thuspositioned, said shell being provided with a longitudinal slot oppositesaid measuring slit and registrable with said transverse bore in thecore to permit the removal of the said thus positioned fuse wire, saidcore being formed with a transverse peripheral groove and a longitudinalgroove running from a point within the outward end of the core into saidperipheral groove, a pin projected from the wall of the shell forengagement in said peripheral and longitudinal grooves for permittingrelative rotation of the shell and core while limiting completewithdrawal of the core from the shell, and a handle on the outward endof the core.

7. A safety fuse plug of the type described comprising a tubular shellhaving one end closed and provided with a screw threaded socket engagingferrule, and an end contact and having its other end open, a coreadapted to be telescoped into said shell, a piece of fuse wire, saidcore having a transverse bore, adapted to receive said fuse wire, saidshell having a transverse measuring slit through which said fuse wire isto be passed with said bore, said fuse wire adapted to be shearedbetween the sides of the core and one edge of said slit for cutting thefuse wire to the re quired length upon inwardly moving the core, saidcore being adapted to be moved further inwardly to bend the end portionsof the cut length of fuse wire and wedge the ends between the core andthe pair of contacts in the I slit and registrable with said transversebore in the core to permit the removal of said positioned fuse wire,said core being formed with a transverse peripheral groove and alongitudinal groove running from a point within the outward end of thecore, into said peripheral groove, a pin projected from the wall of theshell for engagement in said peripheral and longitudinal grooves forpermitting relation rotation of the core from the shell, a handle on theoutward end of the core, a metallic cutting bar at the said one edge ofmaid transverse measuring slit in said shell adapted to cooperate withone edge of the peripheral groove in the core to cut fuse wire of theproper softness only.

In testimony whereof I aflix my signature.

THOMAS WILLIAM 'MERTZ.

